The ability of the retinal pigment epithelium to store vitamin A was tested by injecting mice with retinol acetate or retinol palmitate and examining their retinas and livers using fluorescence and electron microscopy. The results showed clear, dose-related increases in the numbers and sizes of vitamin-A-storing lipid droplets in the stellate cells of the liver. Concomitantly, more conservative increases in similar lipid droplets occurred in the pigment epithelium but not in other cells of the retina. Such lipid droplets may represent physiological sites of vitamin A storage which are important for the maintenance of photoreceptor cells by the retinal pigment epithelium. Electron microscopic histochemistry for catalase demonstrated that peroxisomes, like the putative vitamin-A-storing lipid droplets were distributed along the basal and lateral cell surfaces of the pigment epithelium where receptors for plasma retinol-binding protein have been reported. Peroxisomes may play a role in the reactions related to the esterification and sequestering of vitamin A. BIBLIOGRAPHIC REFERENCES: Enriques, N., Israel, P., Bergsma, D., Robison, W.G., Jr., Whikehart, D. and Chader, G.: Neural retinal and pigment epithelial cells in culture: Patterns of differentiation and effects of prostaglandins and cyclic AMP on pigmentation. Exp. Eye Res. 22: 559-568, 1976. Robinson, W.G., Jr. and Kuwabara, T.: Light-induced alterations of Retinal pigment epithelium in black, albino, and beige mice. Exp. Eye Res. 22: 549-557, 1976.